These extensions have been registered:

  * Firefox: https://addons.mozilla.org/en-US/firefox/addon/disable-slack-wysiwyg/
  * Chrome: https://chrome.google.com/webstore/detail/jenojkbpialbgpbgokiakifhpmoponjn

Based on the script by Kevin Fahy [1] and multiple discussions [2] [3] about Slack's new interface.

Let me know if you have any questions.

  [1]: https://github.com/kfahy/slack-disable-wysiwyg-bookmarklet
  [2]: https://news.ycombinator.com/item?id=21589647
  [3]: https://news.ycombinator.com/item?id=21591950

See also the bookmarklet https://news.ycombinator.com/item?id=21591950